Hello,

The syllabus of UPSC tends to be more humanities oriented, so belonging to science stream the only advantage you can have is going for graduation in mathematics, physics, and chemistry as these subjects come as optional papers, so in that sense you'll already be well acquainted with the syllabus and the optional paper syllabus is equivalent to that of graduation studies only, other than this you have to start the preparation of general studies from the start, read newspaper on a daily basis, go through NCERTs for a strong foundation, and then move towards the standard book, go through previous year paper and apply mock paper and test series regularly to evaluate your preparation level.